Drive systems and devices incorporating drive systems

ABSTRACT

A fixation device may be used for supporting and/or stretching an injured body part. An exemplary fixation device uses a thumb wheel control element to provide controlled rotational micromovements of a joint. The control element and its associated drive system allow for movement along a particular axis, while the position remains fixed with relation to the other axis. In addition, the fixation device may incorporate a drive system that introduces a simultaneous longitudinal translation with rotation, in order to provide for a common point of origin of rotation between the fixation device and the affected body part supported by the fixation device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 11/408,617, which was filed on Apr. 21, 2006, which applicationclaims the benefit of U.S. Provisional Application No. 60/674,052, filedon Apr. 22, 2005, each of which is incorporated herein by reference inits entirety.

FIELD OF THE INVENTION

The disclosed embodiments relate generally to medical device technology,and more specifically to orthopedic fixation devices for treatingcontracture and to the drive systems that allows precise control forpositioning and locking such fixation devices.

BACKGROUND OF THE INVENTION

Oftentimes, injury to a joint or bone can result in contracture, anabnormal tightening or shortening of the muscles and/or ligaments thatmay act to prevent a normal range of motion for the affected body part.Contracture may also be a congenital condition restricting motion.Treatment regimens for contracture typically involve the use of afixation device, such as a splint. The splint mechanism would usually beplaced on the affected patient by medical personnel in such a way as tostretch and/or support the affected body part during the healingprocess, holding the affected body part in the proper position fortreatment.

Treating contracture in joints can prove particularly problematic, sincejoints can undergo a wide range of motion. As a result, a fixationdevice which can accommodate a wide range of motions and which can allowmedical professionals to precisely orient the affected body part may beneeded in order to provide effective treatment options. A typicaltreatment regimen would require repeated visits to medical professionalsso that the fixation device could be periodically adjusted, providingthe necessary orientation to the affected body part and setting theproper amount of stretching and support for healing. So in order toprovide effective treatment, a medical professional needs to be able tointroduce precisely calibrated alterations to the position of thefixation device, and thereby the affected joint.

It is also important that the fixation device support the joint or bonein a way that corresponds to the natural range of motion for thejoint/bone. Conventional fixation devices tend to introduce an unwantedcompression to the joint socket or bone gap, since their point of originfor rotation is offset from that of the joint/bone. As the point ofrotation is not the same for the affected body part and the fixationdevice, the body part is forced to absorb the difference, typically bydeflecting to compress the gap between bones. This may introduceunwanted stress to the joint/bone that is the target of healing, slowingthe healing process and possibly causing additional, unintentionalinjury.

So, there is a need for an improved fixation device that will allowmedical professionals to make effective, calibrated adjustments to thepositioning of the injured body part. Additionally, there is a need fora fixation device that provides for a common point of origin forrotation between the fixation device and the injured body part,preventing unintentional injury and speeding healing by ensuring thatsupported joints/bones are held in a natural alignment position.

SUMMARY

The present application discloses embodiments for a multi-directionaldrive system, typically used to control and fix splint-type elements fora fixation device. The drive system comprises a control element, such asa thumb wheel, and a drive element, such as a drive wheel, coupled tothe control element such that the drive element can be driven to rotateabout a first axis by rotation of the control element. A housingsupports the control element and the drive element. A driven article,such as a substrate, is coupled with the drive element so as to berepositioned by rotation of the drive element.

The direction in which the driven article is repositioned depends onwhether the drive system is in the first or second position. Often, thedrive element has two locking positions, oriented so that they areangularly displaced from each other by ninety degrees, and by switchingbetween the two positions of the drive element, the driven article maybe positioned along one axis without affecting the position of thedriven article along the other axis. This allows for precise orientationof the driven article using the drive element, controlled by the singlecontrol element.

When the drive system is turned to the first position, rotation of thedrive element causes the driven article to move in a first direction,while when the drive system is turned to the second position, rotationof the drive element causes the driven article to move in a seconddirection. And while an exemplary embodiment might have the first andsecond positions angularly displaced from each other by 90°, the axescould be positioned through a wide range of angles. Indeed, alternativeembodiments may allow for a range of motion not simply along two axes,but through a wide range of angles, by allowing the drive element tointeract with the driven article as it pivots throughout its angularrange of motion.

In a typical embodiment, such a drive system might be used to controland fix the movement of two elements of a joint. This would provide asimple and effective means for a medical professional to calibratevarious splint-like elements of a fixation device so that a patient'sjoint may be held in proper alignment. Using a single simple thumb wheelcontrol element, the doctor would be able to position and calibrate theelements of a fixation device with great precision in one direction at atime (while the other direction was held securely in place). This sortof controlled rotational micromovement would assist medicalprofessionals much more in setting the proper alignment than the freerotation provided by common ball-joint systems, by ensuring that onlyintentional actuation would take place.

An external fixation device having a joint that incorporates such adrive system is also disclosed. The external fixation device comprisesfirst and second portions connected by an adjustable joint. Theadjustable joint comprises a drive system that includes a controlelement that can be used to rotate the first portion relative to thesecond portion. The first portion may include a clamp assembly forsecuring the first portion to a bone via one or more bone screws. Theclamp assembly would be capable of being repositioned along alongitudinal axis that extends along the first portion such that theclamp assembly may be moved closer or further from the second portion.

In some embodiments, the position of the clamp assembly can becontrolled by the control element so that the control element cansimultaneously cause rotation of the first portion relative to thesecond portion and translation of the clamp assembly relative to thesecond portion. It may be especially useful to couple simultaneoustranslation in the longitudinal direction with rotation of the injuredbody part. Such an embodiment would allow for a single simple controlelement to provide precisely calibrated positioning of the fixationdevice (to stretch and support an injured body part in order to aid inhealing), while also ensuring natural alignment of the bones byproviding that the fixation device and the bones have a common point oforigin of rotation.

The control element in such a fixation device may be moved between firstand second positions. In the first position, the control element may beoperable to rotate the first portion relative to the second portion in agenerally horizontal plane. In the second position, the control elementcan be operable to rotate the first portion relative to the secondportion in a generally vertical plane. Typically, an integrated lockingmechanism also allows for rotation in only one direction at a time, andfixes the position of the drive element with respect to the drivenarticle of the fixation device when switching between the two positions.This allows for precise calibration of the fixation device without thefear of introducing accidental movement. By using a drive system thatincorporates the teachings of the present disclosure, rotation of thefirst portion in both the generally vertical and horizontal planes canbe accomplished about a common point origin of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example in the accompanyingfigures, in which like reference numbers indicate similar parts, and inwhich:

FIG. 1A shows an elevational view of an embodiment of amulti-directional drive system in a first position;

FIG. 1B shows an elevational view of the multi-directional drive systemshown in FIG. 1A in a second position;

FIG. 2A shows a plan view of an alternative embodiment of a drive wheel;

FIG. 2B shows a cross-sectional view taken along 2B-2B of FIG. 2A;

FIG. 3A shows an elevational view of an alternative embodiment of amulti-directional drive system in a first position;

FIG. 3B shows an elevational view of the multi-directional drive systemshown in FIG. 3A in a second position;

FIG. 3C shows an elevational view of the multi-directional drive systemshown in FIG. 3A with an alternative drive wheel;

FIG. 3D shows a cut-away elevation view of a multi-directional drivesystem with a cylindrical sheath locking mechanism;

FIG. 3E shows an elevation view of an adjustable joint having a keyholedslot for use with a locking multi-directional drive system, such as thatshown in FIG. 3D;

FIG. 4A shows an elevational view of an embodiment of an adjustablejoint having a drive system positioned in a first position;

FIG. 4B shows an elevational view of the adjustable joint shown in FIG.4A, illustrating an example of the rotational motion of the joint;

FIG. 4C shows an elevational view of the adjustable joint shown in FIG.4A having the drive system positioned in a second position;

FIG. 4D shows an elevational view of the adjustable joint shown in FIG.4A with an alternative shaft slot configuration;

FIG. 5 shows a perspective view of an embodiment of a fixation device;and

FIGS. 6A-6C show plan views for explaining the rotational andtranslational action of the fixation device shown in FIG. 5.

DETAILED DESCRIPTION

FIG. 1A shows an embodiment of a multi-directional drive system 100. Thedrive system 100 includes a drive wheel 102, which serves as a driveelement, that can be driven to rotate by rotation of a thumb wheel 106,which serves as a control element. The thumb wheel 106 and the drivewheel 102 are connected by a drive shaft 104. The drive shaft 104 (shownin part with broken lines) extends along a longitudinal axis A-A and isfixed to the thumb wheel 106 such that it rotates about axis A-A as thethumb wheel 106 is rotated. The drive wheel 102 is fixed to the driveshaft 104 and rotates as the drive shaft 104 rotates. Thus, rotation ofthe drive wheel 102 can be controlled directly by rotation of the thumbwheel 106. For example, the drive wheel 102 can be rotated in thedirection indicated by arrow 108 by rotating the thumb wheel in thedirection indicated by arrow 110. Rotating the thumb wheel 106 in theopposite direction causes rotation of the drive wheel 102 in theopposite direction.

The drive wheel 102, drive shaft 104, and thumb wheel 106 are allsupported by a support housing 112. The support housing 112 holds thedrive wheel 102 in place such that, while the drive wheel 102 is free torotate with rotation of the thumb wheel 106, the drive wheel 106 doesnot travel, but instead rotates in place.

The drive wheel 102 is frictionally coupled with a substrate 114 suchthat the substrate 114 is free to move under the influence of a driveforce applied by rotation of the drive wheel 102. For example, rotationof the drive wheel 102 in the direction indicated by arrow 108 drivesthe substrate 114 in a direction that extends into the page as indicatedat 116. Similarly, rotation of the drive wheel 102 opposite to thedirection indicated by arrow 108 drives the substrate 114 in a directionthat extends out of the page. Thus, the substrate 114 in FIG. 1A can bedriven in two directions by rotation of the thumb wheel 106.

The support housing 112 is fixed in position so as to preventtranslational motion of the drive wheel 102. The support housing 112can, however, be rotated about the axis B-B. In one example, the supporthousing 112 can be rotated in the direction indicated by arrow 118 bypushing the thumb wheel 106 in a direction that extends into the page asindicated at 120.

FIG. 1B shows the drive system 100 in a second position, where the drivesystem 100 is rotated 90° compared to the position of the drive system100 as it is shown in FIG. 1A. With the drive system 100 positioned inthis second position, the substrate 114 can be driven in a direction asindicated by arrow 122. With the substrate 114 frictionally coupled withthe drive wheel 102, rotation of the drive wheel 102 in the directionindicated by arrow 124 exerts a force onto the upper surface of thesubstrate 114 causing the substrate 114 to be driven in the directionindicated by arrow 122. The drive wheel 102 can also be rotated in adirection opposite the direction indicated by arrow 124, which wouldcause the substrate 114 to be driven in a direction opposite thedirection indicated by arrow 122.

The drive system 100 shown in FIGS. 1A and 1B provides a mechanicallysimple and efficient mechanism for driving an article in multiplenon-parallel directions. The view shown in FIG. 1A shows the drivesystem 100 in a first position for driving, as an exemplary drivenarticle, substrate 114 in directions that extend in and out of the page.The view shown in FIG. 1B shows the drive system 100 in a secondposition for driving the substrate 114 in directions that extend to theright and to the left across the page. Typically, the drive system 100is capable of being rotated to be disposed in a first or second positionaccording to a desired direction of translation of the substrate 114. Itis contemplated, however, that the drive system 100 could be rotated topositions other than the two positions shown in FIGS. 1A and 1B,allowing for additional, alternative drive vectors.

In FIGS. 1A and 1B the substrate 114 is forced to move due to rotationof the drive wheel 102 provided that sufficient friction exists betweenthe outer surface of the drive wheel 102 and the upper surface of thesubstrate 114. In the absence of sufficient friction, rotation of thedrive wheel 102 may be ineffective for driving the substrate 114. Forexample, inadequate frictional coupling between the drive wheel 102 andthe substrate 114 can result in intermittent or no movement of thesubstrate 114. In this regard, there are several measures that can betaken in order to ensure adequate friction between the drive wheel 102and the substrate 114. The outer surface of the drive wheel 102 and/orthe upper surface of the substrate 114 can be formed of a material, orcoated with a material, that is conducive to providing an adequatefriction joint. For example, surface asperities or other irregularitiesthat increase the friction-joint surface area can be provided on theouter surface of the drive wheel 102 and/or the upper surface of thesubstrate 114.

FIGS. 2A and 2B show an example of how the embodiment shown in FIGS. 1Aand 1B can be modified in order to alter or replace the friction jointbetween the outer surface of the drive wheel 102 and the upper surfaceof the substrate 114. FIG. 2A shows a plan view of a cogged drive wheel202, which serves as an alternative drive element, that can be used witha drive system such as the drive system 100 (in place of the drive wheel102) shown in FIGS. 1A and 1B. FIG. 2B shows a cross-sectional viewtaken along section 2B-2B in FIG. 2A. Note that in the embodiment shownin FIGS. 2A and 2B, several components of the drive system 100 have beenomitted for clarity.

The cogged drive wheel 202 includes a plurality of cogs 206, making itsuitable for driving a substrate 204, which serves as a driven article,having a plurality of holes or recesses 208. As shown in FIG. 2A, thecogs 206 can mate with recesses 208 in order to provide a secure jointfor driving the substrate 204 as the drive wheel 202 rotates. Note thatcharacteristics of the cogs 206 and/or the recesses 208 can vary fromwhat is shown in FIG. 2A. For example, the size, shape, and spacing ofthe cogs 206 and/or the recesses 208 can vary. Preferred arrangements ofthe cogs 206 and recesses 208 will allow for the cogs 206 to fit atleast somewhat into successive recesses 208 as the drive wheel 202rotates.

The cogged drive wheel 202 can be turned about its central axis or hub210 (shown in FIG. 2B) by a drive system, for example drive system 100,in order to reposition the substrate 204. Referring to FIG. 2A, thecogged drive wheel 202 can also be turned, for example as indicated byarrow 212, in order to change the direction that the substrate 204 movesas the drive wheel 202 rotates about hub 210. In a first position (shownin solid lines), the drive wheel 202 can be rotated about hub 210 inorder to reposition the substrate 204 in either of two directions thatextend right and left across the page. The drive wheel 202 can be turnedas indicated by arrow 212 from the first position to a second position(shown in broken lines). In the second position, the drive wheel 202 canbe rotated about hub 210 in order to reposition the substrate 204 ineither of two directions that extend up and down the page. The drivewheel 202 can be turned to be positioned in either of the two positionsshown in FIG. 2A so that the substrate 204 can be repositioned in any offour directions extending up, down, right, and left across the page. Insome embodiments, the drive wheel 202 can be moved away from thesubstrate 204 while it is being turned, particularly if the cogs 206 arearranged such that they would otherwise interfere with the ability ofthe wheel 202 to be turned.

FIGS. 3A and 3B show a drive system 300 which can serve as analternative embodiment to drive system 100. The drive system 300includes a cogged drive wheel 302, which serves as a drive element, thatcan be driven to rotate by rotation of a thumb wheel 306, which servesas a control element. The thumb wheel 306 and the drive wheel 302 areconnected by a gear system 304. In one embodiment, the gear system 304includes a worm gear 308, which includes a worm 309 and a worm wheel310. The gear system 304 also includes a gear 312 fixed to the wormwheel 310 for driving the drive wheel 302.

The thumb wheel 306 is connected to the worm 309 of the worm gear 308via a shaft 314. The shaft 314 translates rotation of the thumb wheel306 to the worm 309 so that the worm 309 rotates according to rotationof the thumb wheel 306. The worm 309 meshes with teeth 316 of the wormwheel 310. As the worm 309 is rotated, it exerts a force againstsuccessive teeth 316 of the worm wheel 310 resulting in rotation of theworm wheel 310 about its hub 318. The gear 312 is fixed to the wormwheel 310 such that the gear 312 rotates about the hub 318 as the wormwheel 310 rotates about the hub 318. The gear 312 has teeth 320 thatmesh with cogs 322 of the drive wheel 302. As the gear 312 rotates,successive teeth 320 exert a force against successive cogs 322 of thedrive wheel 302 causing the drive wheel 302 to rotate about hub 324.Thus, rotation of the drive wheel 302 can be controlled by rotation ofthe thumb wheel 306. For example, the drive wheel 302 can be rotated inthe direction indicated by arrow 326 by rotating the thumb wheel 306 inthe direction indicated by arrow 328. Rotating the thumb wheel 306 inthe opposite direction causes rotation of the drive wheel 302 in theopposite direction.

The drive wheel 302, gear system 304, shaft 314, and thumb wheel 306 areall supported by the drive housing 330. The support housing 330 holdsthe drive wheel 302 in place such that, while the drive wheel 302 isfree to rotate about hub 324 with rotation of the thumb wheel 306, thedrive wheel 306 does not travel, but instead rotates in place.

The drive wheel 302 is coupled with a substrate 332, which serves as adriven article, via the cogs 322 of the drive wheel 302 that can meshwith recesses 334 formed in a surface of the substrate 332. An optionalresilient member 336 can be provided for biasing the drive wheel 302towards the substrate 332. The resilient member 336 can be, for example,a spring. The resilient member 336 allows for the drive wheel 302 to bewithdrawn from the surface of the substrate 332 as necessary, forexample in order to turn the drive wheel 302.

The substrate 332 is disposed such that it is free to move under theinfluence of a drive force applied by rotation of the drive wheel 302.Rotation of the drive wheel 302 in the direction indicated by arrow 326drives the substrate 332 in a direction indicated by arrow 338.Similarly, rotation of the drive wheel 302 opposite to the directionindicated by arrow 326 drives the substrate 332 in a direction oppositethe direction indicated by arrow 338. Thus, the substrate 332 can bedriven in two directions by rotation of the thumb wheel 306.

The support housing 330 is fixed in position so as to preventtranslational motion of the drive wheel 302. The support housing 330can, however, be rotated about the axis C-C. The support housing 330 canbe rotated in the direction indicated by arrow 340 by pushing the thumbwheel 306 in a direction that extends into the page as indicated at 342.

FIG. 3B shows the drive system 300 in a second position, where the drivesystem 300 is rotated 90° compared to the position of the drive system300 as it is shown in FIG. 3A. With the drive system 300 positioned inthis second position, the substrate 332 can be driven in a directionthat extends in and out of the page. With one or more recesses 334 ofthe substrate 332 meshed with a cog or cogs 322 of the drive wheel 302,rotation of the drive wheel 302 in the direction indicated by arrow 344causes the substrate 332 to be driven in a direction that extends intothe page as indicated at 346. Note that rotation of the drive wheel 302in the direction indicated by arrow 344 can be generated by rotating thethumb wheel 306 in the direction indicated by arrow 348. The drive wheel302 can also be rotated in a direction opposite the direction indicatedby arrow 344, which would cause the substrate 332 to be driven in adirection that extends out of the page and opposite the directionindicated at 346.

FIG. 3D illustrates another optional element that can be used inconjunction with the basic mechanisms shown in FIGS. 3A and 3B.Specifically, FIG. 3D illustrates an embodiment with an incorporatedlocking mechanism 380 designed to engage the substrate 332 to preventunwanted movement. In general, incorporating a locking mechanism 380within the drive system 300 provides for controlled rotationalmicromovements that occur only through intentional actuation of thedrive system 300; driven elements would not be allowed to rotate freelywith respect to one another, but would be locked so that they may onlyrotate in a single direction at once based upon movements of the controlelement 306. In other words, whenever the drive system 300 is notengaged with the substrate 332 of the driven article (as for example,when the drive system 300 is pivoting between positions), the lockingmechanism 380 would hold the driven article in place relative to thedrive system 300.

In the disclosed embodiment, the locking mechanism 380 comprises acylindrical sheath 381 disposed about the drive system 300. The cylinder381 has teeth 382 along its bottom edge, which mesh with the recesses334 of the substrate 332 to prevent motion of the substrate 332 wheneverthe locking mechanism 380 is engaged. A spring mechanism 386 may providethe downward force of engagement for the disclosed locking mechanism380.

In this embodiment, the spring 386 holds the cylinder 381 in placeagainst the substrate 332 whenever the drive system 300 is pivotingbetween positions. The shaft 314 may operate as both the driving rod forthe gears and a lever for engaging/disengaging the locking mechanism380. By way of example, the shaft 314 may include a hinge 384, thatallows it to pivot upward and downward in relation to the substrate 332in order to effect engagement. The shaft 314 may pivot to force thelocking mechanism 380 away from the substrate 332, while bringing thedrive system 300 into engagement with the substrate 332. Likewise, theshaft 314 can be used to bring the locking mechanism 380 into engagementwith the substrate 332 while forcing the drive system 300 away from thesubstrate 332 (as for example, when preparing to pivot the drive system300 between its two positions). The engagement of both the lockingmechanism 380 and the drive system 300 can be assisted by a springmechanism 386.

And when such a drive system 300 is used within a joint element 390 (asdescribed below), a slot 393 within the joint housing 391 can be shapedto aid in both the engagement and disengagement of the locking mechanism380. Such a slot 393 for a joint housing 391 is illustrated in FIG. 3E,which shows a slot 393 with a keyhole offset 395 that may be used inconjunction with the shaft 314 to guide the locking mechanism 380between positions. By way of example, if the shaft 314 of the drivesystem 300 is moved into the keyhole 395, it acts as a lever todisengage the locking mechanism 380 from the substrate 332 and to engagethe drive system 300. To do so effectively, the shaft 314 may have anotch that allows it to enter into the keyhole 395 when depressedtowards the center of the joint housing 391. Alternatively, whenever theshaft 314 is located anywhere in the slot 393 (rather than the keyhole395, the locking mechanism 380 would be engaged and the drive system 300would be capable of being rotated to either 90° position.

Such a locking mechanism 380 could also be used with a frictionalcoupling drive system, such as that of FIGS. 1A and 1B, and wouldoperate similarly except for the use of frictional engagement of thecylinder with the substrate 332 rather than employing teeth 382 toengage recesses 334 in the substrate 332. Persons skilled in the artfield will appreciate that other types of locking mechanisms 380 couldalso be used to lock the substrate 332 in place whenever the position ofthe drive system 300 is altered. The locking mechanism 380 of FIG. 3D issimply one example; any equivalent locking mechanisms are includedwithin the scope of this disclosure.

Thus, a difference between the drive system 100 shown in FIGS. 1A and 1Band the drive system 300 shown in FIGS. 3A and 3B is that the drivesystem 300 includes a gear system (gear system 304) between the thumbwheel 306 and the drive wheel 302. While the drive system 100 is shownas a friction-drive system and the drive system 300 is shown as acogged-wheel drive system, these aspects of the two embodiments can beconsidered interchangeable. That is, the drive system 100 can be readilymodified to include a cogs on the drive wheel 102 and the drive system300 can be readily modified to have drive wheel 302 free of the cogs322. Also, it will be noted that the cross-sectional shape of the drivenarticle can vary. The drive system 100 and the drive system 300 can beused with a substrate or driven article having a substantially planarcross-section, for example as shown in FIGS. 1A and 1B, or asubstantially non-planar cross-section, for example as shown in FIGS. 3Aand 3B, or other planar or non-planar shapes.

The view shown in FIG. 3A shows the drive system 300 in a first positionfor driving, as an exemplary driven article, substrate 332 in directionsthat extend to the right and to the left across the page. The view shownin FIG. 3B shows the drive system 300 in a second position for drivingthe substrate 332 in directions that extend in and out of the page. Thedrive system 300 can be rotated to be disposed in the first or secondposition according to a desired direction of translation of thesubstrate 332. It is contemplated that the drive system 300 could berotated to positions other that the two positions shown in FIGS. 3A and3B, allowing for additional, alternative drive vectors.

FIG. 3C shows a drive system 350, which is similar to the drive system300 except that a friction-drive wheel 102 (shown in FIGS. 1A and 1B) isused in place of the cogged drive wheel 302. Also, a wheel 352 is usedin place of the gear 312 for rotating the drive wheel 102. The wheel 352is fixed to worm wheel 310 and frictionally coupled with the drive wheel102. Thus, rotation of the thumb wheel 306 causes rotation of the drivewheel 102 via the worm gear 308 and the wheel 352. The drive wheel 102is frictionally coupled with the surface of the substrate 354, whichserves as a driven article. The outer surface of the drive wheel 102and/or the upper surface of the substrate 354 can be formed of amaterial, or coated with a material, that is conducive to providing anadequate friction joint.

Turning next to FIGS. 4A-4C, an adjustable joint 400 will be describedthat incorporates a drive system such as any of the embodimentsdescribed herein. Such an adjustable joint 400 would be useful, by wayof example, in positioning the elements of a fixation device, allowingfor precise, calibrated movements in order to provide proper alignmentof the fixation device (and thereby the injured body part) for healing.One feature of the adjustable joint 400 is that it allows for rotationof one element relative to another element in two different planes abouta common origin of rotation. The joint 400 comprises a housing 402 and asocket member 404. The view shown in FIG. 4A includes a partiallycut-away view of socket member 404 for purposes of clarity. The housing402 at least partially houses a drive system 406. Any of the drivesystems 100, 300, or 350, or equivalents thereof can be used as thedrive system 406. In the illustrated embodiment, the drive system 406includes a thumb wheel 408, which serves as a control element, and aworm 410 connected by a shaft 412. The drive system 406 also includes adrive wheel 414, which serves as a drive element. The drive wheel 414 isrotated by rotation of the thumb wheel 408. The drive wheel 414 isfrictionally coupled with a contact surface 416 of the socket member 404such that rotation of the thumb wheel 408 causes the surface 416 to moverelative to the drive wheel 414.

As oriented in the view shown in FIG. 4A, the housing 402 has a loweredge 418 that fits inside the socket member 404 below an upper edge 420of the socket member 404. The outer diameter of the lower edge 418 islarger than the inner diameter of the upper edge 420 so that the socketmember 404 and housing 402 can be held together. Similarly, alternativeconfigurations could be employed to form the adjustable joint 400. Onealternative, by way of example, would be to essentially reverse theconfiguration set forth above, with the socket formed having an upperedge that would fit inside the housing above the lower edge of thehousing and the diameter of the upper edge being larger than the innerdiameter of the lower edge.

Referring additionally now to FIG. 4B, the socket member 404 can berotated relative to the housing 402. The angular displacement of thesocket member 404 is controlled by rotating the thumb wheel 408. Forexample, as shown in FIG. 4B, by rotating the thumb wheel 408 in thedirection indicated by arrow 422 the socket member 404 can be rotatedfrom the position shown in solid lines to an angularly displacedposition shown in broken lines in the direction indicated by arrow 424.The socket member 404 can also be rotated, for example from the positionshown in broken lines to the position shown in solid lines, in adirection opposite the direction indicated by arrow 424 by rotating thethumb wheel 408 in a direction opposite the direction indicated by arrow422.

Thus, in the arrangement shown in FIGS. 4A and 4B, the socket member 404can be angularly displaced in a first plane in directions that extendleft and right across the page by rotation of the thumb wheel 408. Thedrive system 406 can be turned approximately 90° from the position shownin FIGS. 4A to the position shown in FIG. 4C. A shaft slot 426 providesclearance for the shaft 412 to move between the position shown in FIG.4A to the position shown in FIG. 4C. With the drive system 406 in theposition shown in FIG. 4C, the socket member 404 can be angularlydisplaced in a second plane in directions that extend in and out of thepage by rotation of the thumb wheel 408. For example, by rotating thethumb wheel 408 in the direction indicated by arrow 428 the socketmember 404 can be rotated in the direction indicated at 430 to anangularly displaced position. The socket member 404 can also be rotatedin a direction opposite the direction indicated at 430 by rotating thethumb wheel 408 in a direction opposite the direction indicated by arrow428.

Thus, as will be appreciated by the views provided in FIGS. 4B and 4Cand the description provided above, an adjustable joint can be realizedthat allows for rotation of one element relative to another element intwo different planes about a common origin of rotation. For example, inthe configuration shown in FIG. 4B the socket member 404 can be rotated(relative to the housing 402) in a first plane, while in theconfiguration shown in FIG. 4C the socket member 404 can be rotated(relative to the housing 402) in a second plane that is generallyorthogonal to the first plane. In both of FIGS. 4B and 4C, the socketmember 404 rotates about a common origin of rotation.

FIG. 4D shows an adjustable joint 450 that is similar to the adjustablejoint 400 except that the shaft slot 426 is replaced with a curved shaftslot 452. The curved shaft slot 452 forces the drive system 406 to moveaway from the socket member 404 as the drive system 406 is turnedbetween the two positions shown in FIGS. 4A and 4C. As the drive system406 is being turned, the shaft 412 rides the contour of the curved slot426. The remaining components of the drive system 406 remain fixedrelative to the position of the shaft 412, so as the shaft 412 is movedaway from the socket member 404 and back by the contour of the curvedslot 452 the balance of the drive system 406 is moved as well.

Moving the drive system 406 away from the socket member 404 can ease theeffort required for turning the drive system 406 by reducing thefriction between the drive wheel 414 and the surface 416 (shown in FIG.4A) that would otherwise oppose the turning of the drive system 406.Although not shown, in some embodiments, a cylindrical-like mechanismmay be disposed inside the housing 402 and around the drive system 406for temporarily holding the socket member 404 in place as the drivesystem 406 is being turned or as a locking mechanism when the desireddisplacement of socket member 404 is obtained. In practice, the shaft412 would force the cylindrical-like mechanism, or locking cylinder,against the socket member 404 to hold the socket member in place. By wayof example, a locking mechanism such as that shown in FIGS. 3D and 3Ecould be employed.

The adjustable joints 400 and 450 of the disclosed embodiments can beused in any system where a rotatable joint is desired, particularly if ajoint is desired that can be controlled to rotate in multiple dimensionsabout a single axis of rotation. Such a joint allows for simple yetprecise control of the movements of the joint elements (typically asocket member and a joint housing), and may be useful in a wide range ofmedical devices. By way of a specific example, such a joint may proveuseful within a fixation device, of the type described below, byallowing for precise orientation of the injured body part for healing.

Turning next to FIG. 5, a view of an external fixation device 500 isshown that incorporates teachings of the present disclosure. Forexample, the device 500 can be attached to a patient's arm and hand (notshown) for treating a wrist contracture. Such an external fixationdevice 500 may be used to treat a wide variety of contractures inskeletal joints, either congenital or acquired. However, fixationequipment and methods incorporating teachings of the present disclosuremay be used in other orthopedic applications including, but not limitedto, fractures and bone lengthening. External fixation device 500 may besatisfactorily used to treat a wide variety of orthopedic indications. Afixation device incorporating teachings of the present disclosure may beformed from a wide variety of materials. For some applications externalfixation device 500 may be formed from aluminum and/or stainless steelor other metal alloys satisfactory for use in treating orthopedicindications. For other applications various components and partsassociated with external fixation device 500 may be formed from highstrength composite materials and/or cermets.

The particular embodiment of the fixation device 500 shown in FIG. 5 isdesigned to accomplish two separate but related goals. First, it employsa control-drive system allowing for the type of precise and calibratedmovements needed to allow medical professionals to properly orient thefixation device 500 to stretch and/or support an injured body part inthe proper orientation for healing. This precise control allows foreffective initial orientation of the fixation device 500, as well assimplifying any periodic re-orientation of the fixation device 500throughout the treatment process. In addition, the disclosed embodimentimproves the effectiveness of the fixation device 500 by allowing fornatural bone alignment despite the rotation introduced by the fixationdevice 500. It may maintain a common point of origin of rotation forboth the fixation device 500 and the injured body part, thus preventingany unwanted compression forces upon the bone that could delay healing.

Accordingly, the fixation device 500 disclosed below can be configuredto address either or both of these goals, thereby assisting in thehealing process. While the embodiment illustrated in FIG. 5 is designedto accomplish both goals simultaneously, those skilled in the art willunderstand that the fixation device may be configured to accomplisheither of these purposes alone as well. Furthermore, persons skilled inthe art will recognize that FIG. 5 discloses but one, exemplaryembodiment of such a fixation device. These and all other equivalentembodiments are intended to be included within the scope of thedisclosure.

In the disclosed embodiment of FIG. 5, external fixation device 500includes a first portion 502 and a second portion 504 connected by anadjustable joint 506. For example, the adjustable joint 400 or 450described herein can be used as the adjustable joint 506. The adjustablejoint 506 can thus be used to position the first portion 502, whichserves as a driven article, relative to the second portion 504 asdesired. For example, the first portion 502 can be rotated orarticulated as desired relative to the second portion 504, for exampleas shown in FIGS. 4B and 4C.

The first portion 502 includes a clamp assembly 508 for securing a pairof bone screws 510 and 512. The second portion 504 can also, in someembodiments, be provided with a clamp assembly and bone screws (notshown) substantially identical or different to those provided for thefirst portion depending on the application. The first portion 502 alsoincludes a housing 514 having a generally elongated rectangularconfiguration. A drive screw 516 is disposed within the housing 514. Insome embodiments, the second portion 504 can also be provided with ahousing and drive screw (not shown) substantially the same as thoseprovided for the first portion or substantially different depending onthe application.

The housing 514 includes an elongated slot or opening 518. The drivescrew 516 can be rotatably disposed within the elongated slot 518.Threads 520 are formed on the exterior of the drive screw 516 andengaged with the clamp assembly 508 whereby rotation of the drive screw516 will result in longitudinal movement of the clamp assembly 508relative to the adjustable joint 506 and the second portion 504.

The adjustable joint 506 rotatably connects the first and secondportions 502 and 504. In the embodiment shown in FIG. 5, the adjustablejoint 506 allows for controlled rotation of the first portion 502 in agenerally horizontal plane relative to the second portion 504 which alsocorresponds generally with a plane extending through bone screws 510 and512. The adjustable joint 506 also allows for controlled rotation of thefirst portion 502 in a generally vertical plane relative to the secondportion 504 which also corresponds generally with movement perpendicularto the plane extending through the bone screws 510 and 512.

The adjustable joint 506 includes a drive system 522 for providingdesired controlled rotation or articulation of the first portion 502relative to the second portion 504. Any of the drive systems 100, 300,or 350, or equivalents thereof can be used as the drive system 522. Thedrive system 522 includes a thumb wheel 524, which serves as a controlelement, and a shaft 526. The thumb wheel 524 and shaft 526 can be movedbetween a first position (shown in solid lines) and a second position(shown in broken lines) for turning the drive system 522. In the firstposition, the thumb wheel 524 can be rotated for rotating the firstportion 502 in the generally horizontal plane. In the second position,the thumb wheel 524 can be rotated for rotating the first portion 502 inthe generally vertical plane. In this way, the use of the adjustablejoint 506 in conjunction with the drive system 522 and thumb wheel 524improves control over the positioning of the elements of the fixationdevice 500.

It may also be beneficial to structure the drive system 522 so that acommon point of origin if rotation is maintained. Generally, this wouldbe accomplished by providing for simultaneous longitudinal translationaccompanying any rotation, in order to ensure that no compression forcesare inadvertently introduced to the injured body part. By way ofexample, the drive system 522 can also be used to rotate a drive screw516 (in addition to orienting the first portion 502 of the fixationdevice 500 with respect to the second portion 504), resulting inlongitudinal translation of the clamp assembly 508 and the bone screws510 and 512 as indicated by arrows 528. In other words, turning thethumb wheel 524 can result in simultaneous rotation of the first portion502 and translation of the clamp assembly 508 and bone screws 510 and512. Accordingly, the external fixation device 500 generally utilizesthe motion between the first portion 502 and the second portion 504 torotate the drive screw 516. In this regard, rotation of the drive screw516 may be considered an indirect result of turning the thumb wheel 524.

The simultaneous rotation of the first portion 502 and translation ofthe bone screws 510 and 512 is preferable for reasons described withreference to FIGS. 6A-6C. Referring first to FIG. 6A, an axis D-D isshown that represents a longitudinal axis of the first portion 502. Abone screw 600 is shown for fixing the first portion 502 of the fixationdevice 500 (not shown in FIGS. 6A-6C) to a first bone 608. A firstorigin of rotation point 602 represents a point about which the fixationdevice 500 rotates when the joint 506 is controlled for rotating thefirst portion 502 in the generally horizontal plane. An origin ofrotation point 604 represents the natural origin of rotation for a joint606 between the first bone 608 and a second bone 610. Note that thefirst and second origin points 602 and 604 are offset by a fixeddistance X, which remains fixed for each of the FIGS. 6A-6C.

FIG. 6B shows the results of the adjustable joint 506 rotating the firstportion 502 by an angle a about the first point 602 in the generallyhorizontal plane. In this case, the distance between the point 602 andthe bone screw 512 remained fixed while the first portion 502 wasrotated. As a result, rotation about the point 602 of the adjustablejoint 506 causes compression of the bone gap at the joint 606.

FIG. 6C, on the other hand, shows the results of rotating the firstportion 502 in the same manner as it is rotated in FIG. 6B except thatthe bone screw is translated in the direction indicated by arrow 612 bya distance δ. In other words, while the first portion 502 was rotatingby the angle α, the bone screw 512 was translating such that thedistance between the point 602 and the bone screw 512 increased by thedistance δ. Translating the bone screw 512 while the first portion 502is rotating effectively transfers the origin of rotation to point 604 sothat the rotation of the bone 608 can be maintained about the naturalorigin of rotation for the joint 606. Preferably the amount oftranslation δ of the bone screw 512 is determined based on the followingrelationship:

δ=X cos(α)  Equation (1)

Thus, the desired amount of translation δ can be determined based on afunction of the amount of rotation α of the adjustable joint 506 and theoffset X between the first and second origin of rotation points 602 and604.

Turning back to FIG. 5, the drive system 522 can be coupled with thedrive screw 516, for example via a gear system (not shown), so that thedrive screw 516 rotates as the thumb wheel 524 is rotated. This allowsfor longitudinal translation of the clamp assembly 508, and thus of thebone screws 510 and 512, as the first portion 502 is rotated. Preferablythe drive screw 516 is set to rotate such that the clamp assembly 508moves according to equation (1) shown above, where X is the distancebetween the origin of rotation of the adjustable joint 506 and thenatural origin of rotation of a joint (e.g., joint 606) and α is theangle by which the first portion 502 is rotated relative to the secondportion 504.

Thus, turning the thumb wheel 524 can result in simultaneous rotation ofthe first portion 502 and translation of the clamp assembly 508 and bonescrews 510 and 512 such that a joint 606 is rotated about its naturalorigin of rotation 604. So in the exemplary embodiment of FIG. 5, asingle fixation device 500 incorporates a fine control-drive mechanismwhich provides for simultaneous translation while introducing rotation(ensuring proper alignment and natural support for the injured bodypart). While the drive system 522 and the use of simultaneoustranslation in conjunction with rotation of the fixation device 500 maybe used separately, it is particularly beneficial to combine both ofthese elements into a single device.

While various embodiments in accordance with the principles disclosedherein have been described above, it should be understood that they havebeen presented by way of example only, and are not limiting. Forexample, control elements other than a thumb wheel and drive elementsother than a drive wheel are contemplated. Thus, the breadth and scopeof the invention(s) should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with theclaims and their equivalents issuing from this disclosure. Furthermore,the above advantages and features are provided in described embodiments,but shall not limit the application of such issued claims to processesand structures accomplishing any or all of the above advantages.

Additionally, the section headings herein are provided for consistencywith the suggestions under 37 CFR 1.77 or otherwise to provideorganizational cues. These headings shall not limit or characterize theinvention(s) set out in any claims that may issue from this disclosure.Specifically and by way of example, although the headings refer to a“Field of Invention,” such claims should not be limited by the languageunder this heading to describe the so-called technical field. Further, adescription of technology in the “Background of the Invention” sectionis not to be construed as an admission that technology is prior art toany invention(s) in this disclosure. Neither is the “Summary” to beconsidered a characterization of the invention(s) set forth in issuedclaims. Furthermore, any reference in this disclosure to “invention” inthe singular should not be used to argue that there is only a singlepoint of novelty in this disclosure. Multiple inventions may be setforth according to the limitations of the multiple claims issuing fromthis disclosure, and such claims accordingly define the invention(s),and their equivalents, that are protected thereby. In all instances, thescope of such claims shall be considered on their own merits in light ofthis disclosure, but should not be constrained by the headings set forthherein.

What is claimed is:
 1. A method for adjustably supporting an injuredbody part with an external fixation device having a first portionrotatably attached to a second portion, comprising the steps of:removably attaching the first portion of the external fixation device toa bone at a fixed distance from the bone; rotating the first portion ofthe fixation device with respect to the second portion of the fixationdevice; and providing longitudinal translation of the point ofattachment of the first portion of the fixation device to the bone sothat the external fixation device and the bone have a common point oforigin of rotation.
 2. A method as in claim 1, wherein the amount oflongitudinal translation approximates the product of the fixed distancebetween the first portion of the fixation device and the bone and thecosine of the amount of rotation of the first portion with respect tothe second portion of the fixation device.
 3. A method as in claim 2,wherein the rotation of the first portion with respect to the secondportion and the longitudinal translation occur simultaneously.
 4. Amethod as in claim 2, wherein the rotation of the first portion of thefixation device with respect the second portion of the fixation deviceoccurs in one plane; the method further comprising the step of rotatingthe first portion of the fixation device with respect to the secondportion of the fixation device in a second plane.
 5. A method as inclaim 4, wherein the second plane of rotation is substantiallyorthogonal to the first plane of rotation.
 6. A method as in claim 5,wherein the fixation device further comprises a control element, themethod further comprising the steps of: moving the control elementbetween two positions in order to switch between the two planes ofrotation of the first portion with respect to the second portion; andadjusting the control element in order to rotate the first portion withrespect to the second portion and to cause longitudinal translation ofthe point of attachment of the first portion of the fixation device tothe bone.
 7. A method for adjusting a fixation device with a firstportion and a second portion rotatably connected by an adjustable joint,using a control element, comprising the steps of: releasably attachingthe first portion of the fixation device to a bone with a bone screw;and adjusting the control element of the adjustable joint in order tosimultaneously rotate the first portion relative to the second portionand translate the position of the bone screw relative to the secondportion.
 8. A method as in claim 7, wherein the bone screw islongitudinally translated along the length of the first portion, andwherein the first portion is held a fixed distance from the bone.
 9. Amethod as in claim 8, wherein the amount of longitudinal translationapproximates the product of the fixed distance of the first portion fromthe bone and the cosine of the amount of rotation between the firstportion and the second portion.
 10. A method as in claim 9, wherein thecontrol element is capable of being moved between two positionscorresponding to two planes of rotation for the first portion withrespect to the second portion.
 11. A method as in claim 10, wherein thefirst plane of rotation is substantially orthogonal to the second planeof rotation.
 12. A method of adjusting a fixation device that includesfirst and second portions connected by an adjustable joint with acontrol element capable of moving between at least two positions, themethod comprising the steps of: adjusting the control element of theadjustable joint in order to rotate the first portion relative to thesecond portion in a first plane about an origin of rotation;repositioning the control element; and adjusting the control element inorder to rotate the first portion relative to the second portion in asecond plane about the origin of rotation, the second plane beingsubstantially orthogonal to the first plane.
 13. A method as in claim12, wherein the first portion is removably attached to a bone a fixeddistance from the bone, further comprising the step of longitudinallytranslating the point of attachment.
 14. A method as in claim 13,wherein longitudinal translation accompanies rotation of the firstportion with respect to the second portion so that the fixation deviceand the bone have a common point of origin of rotation.
 15. A method asin claim 14, wherein the amount of longitudinal translation approximatesthe product of the fixed distance of the first portion from the bone andthe cosine of the amount of rotation between the first portion and thesecond portion.
 16. A method as in claim 12, further comprising the stepof locking the position of the first portion with respect to the secondportion whenever the control element is repositioned.
 17. A method as inclaim 16, further comprising the step of locking the position of thefirst portion with respect to the second portion once the first portionhas been rotatably adjusted relative to the second portion in bothplanes of rotation.